Encoding and recognition after traumatic brain injury: Neuropsychological and functional magnetic resonance imaging findings

Abstract

Although impairment of episodic memory is common after traumatic brain injury (TBI), the complex nature of human memory suggests the need to study more than recall alone. For this reason, we are presenting an extension with additional analyses of persons reported in a previous publication (Russell et al., 2011). We examined both the encoding and recognition components of an episodic memory paradigm containing both word and letter string blocks using fMRI and neuropsychological testing. This paradigm was completed by 12 persons with complicated mild, moderate, or severe TBI and 12 matched uninjured controls. Comparisons were made between groups and stimulus types. While task behavioral performance was not significantly different between groups, imaging results showed greater activation for the TBI group during the encoding portion of the task, while the control group exhibited more activation on the recognition portion. Observed areas of activation suggest that the TBI group may have used a less effective, but more automatic verbal strategy for encoding the non-pronounceable letter strings, while controls may have opted for more of a recognition-focused strategy. Group differences in CVLT-II performance supported these ideas and further neuropsychological testing also suggested limitations in executive functioning in the TBI group that may have influenced performance. Implications for intervention are discussed.

Neural correlates of visual memory in patients with diffuse axonal injury

“…This finding is in accordance with previous studies of memory in patients with TBI and theoretical models proposing that memory problems in patients with TBI involve the alteration of multiple systems [25,32]. Along these lines, it has been suggested that memory deficits in this population may result from difficulties in the application of active or effortful strategies in learning or retrieval processes [4,51]. Moreover, the involvement of numerous regions in memory performance in this population might indicate the use of compensatory mechanisms to optimize performance [52,53].…”

“…Furthermore, both structures have been associated with visual recognition memory in previous studies of healthy individuals and patients with temporal lobe damage [47,[49][50][51][53][54][55][56][57][58][59][60].…”

Corpus Callosum Integrity and Neuropsychological Performance After Traumatic Brain Injury

“…In keeping with this aim, the DTI analyses presented here were conducted as part of a larger study including FMRI, DTI, and both standardized neuropsychological tests and experimental tests designed for measuring cognitive functioning as part of the fMRI paradigm. 48,49 Our aims in the current study included analysis of DTI parameters within the CC, as well as the examination of how any changes observed may interact with not just cognition in general, but with distinct aspects of memory and executive functioning abilities.…”

“…48,49 Briefly, participants were presented with two dimensional pictures and words as well as control tasks, and asked to judge whether each individual object was pleasant or not based on their own criteria (encoding). Immediately after completion of each encoding block, participants were presented with a mixed block of previously seen objects along with new items, and asked to differentiate between “new” and “old” items (recognition).…”

“…48,49 DTI data were acquired on a Siemens 3T Allegra scanner using echo-planar imaging (EPI) sequences (matrix= 128×128×34, FOV 200, slice thickness 3mm) consisting of seven transaxial images collected in 6 gradient directions at a b-value of 850 with one b=0 weighted image. Structural scans acquired during these sessions included axial T2 weighted images (39 contiguous 3mm slices, TR = 6440 ms, TE = 73 ms, 256 × 256 matrix, FOV = 200mm, flip angle = 150°) and a sagittal 3-D MPRAGE sequence (224 contiguous 0.78 mm slices, TR = 1680ms, TE = 2.48ms, 256×256 matrix, FOV = 200mm, flip angle = 8°).…”